Known fill level measuring devices that use electromagnetic waves to measure fill levels comprise electronics that generate the electromagnetic waves. The generated electromagnetic waves are then guided to the antenna, for example by means of a coaxial conductor, and are coupled into the antenna by way of a corresponding coupling device.
For example from US20030141940A1 and US20030168674A1 two microstrip-waveguide transitions are known, in which in each case the high-frequency substrate together with a coupling element reaches into a waveguide. However, in the case of both these documents the waveguide may have to be closed with a resonator on the other side of the printed circuit board. This resonator may have to be very precisely aligned.
In order to reduce the dimensions of the arrangement (with identical focusing of the radiation transmitted by the antenna) it may be desirable to increase the frequency of the generated electromagnetic waves. However, as a result of this there may be increased demands on the electronics that generate the electromagnetic waves, and on the receiving- and evaluation units. In particular, in this arrangement it may be important to achieve neat coupling or decoupling of the electromagnetic waves to be transmitted to or received from, in or from the waveguide that connects the antenna to the electronics.
According to one exemplary embodiment of the present invention a waveguide transition for a fill level radar is stated, with the waveguide transition comprising a multilayer printed circuit board, a feed line for conducting electromagnetic waves, and a decoupling unit that comprises a coupling element and a resonance space for decoupling the electromagnetic waves from the feed line to a waveguide, wherein the resonance space is integrated in the printed circuit board.
Accordingly, the waveguide transition thus comprises a coupling device that is integrally embedded in the printed circuit board. There is no need for an external resonator. Instead, decoupling of the electromagnetic waves from the feed line to the waveguide takes place directly within the printed circuit board. By integrating the decoupling device in the printed circuit board, integral production of the decoupling unit may take place during the production process or during processing of the printed circuit board. Since no external resonator has been provided for the decoupling unit there may be no problems with mechanical tolerances that may occur when the resonator is attached to the printed circuit board.
The printed circuit board may comprise several conductor planes, which are interconnected by way of electrical leadthroughs and which may carry corresponding electronic components.
This may provide improved decoupling or coupling of a high-frequency wave from a conductor to a waveguide.
According to a further exemplary embodiment of the present invention the printed circuit board comprises a first layer and a second layer, wherein the decoupling unit is integrated in the first layer, wherein the second layer comprises an insulating material, and wherein the second layer is arranged above the first layer so that it covers the decoupling unit.
According to a further exemplary embodiment of the present invention the waveguide transition further comprises a third layer that is arranged between the first layer and the second layer, wherein the first layer is an insulating printed circuit board substrate material, and wherein the third layer is a thin metallization coating.
According to this exemplary embodiment of the present invention the insulating printed circuit board substrate material, in which the resonator of the decoupling unit is located, may be coated by a metallization coating. On this metallization coating the second layer may be arranged in a plate-shaped manner. In this way a sandwich may be formed by the printed circuit board substrate and the second layer, between which a metallization coating is arranged. This metallization coating may not only serve as a mass area for a microstrip line on the second layer, but also as a waveguide wall in the resonator of the decoupling unit.
According to a further exemplary embodiment of the present invention the first layer is metallic.
In this case there may be no need to provide metallization in the form of a third layer.
According to a further exemplary embodiment of the present invention the decoupling unit is designed as a coupling element in conjunction with a resonator.
The resonator may be a hollow space in the first layer, which hollow space is for example generated by an etching process, a milling process, a drilling process or the like.
According to a further exemplary embodiment of the present invention the depth of the resonator corresponds to the thickness of the first layer.
In this case the hollow space of the resonator may for example simply be drilled out of the first layer (in the form of a drilled through-hole in the first layer), or the first layer may simply be etched through completely.
According to a further exemplary embodiment of the present invention the second layer is a high-frequency substrate.
The above may, for example, be a Rogers RT DUROID™ (PTFE composite material) substrate. It may thus be possible to couple high-frequency waves, which propagate within the second layer, into the resonator so that subsequently they may be coupled into the waveguide (which is for example an external waveguide).
According to a further exemplary embodiment of the present invention the first layer is a high-frequency substrate.
According to a further exemplary embodiment of the present invention the resonator is filled with a dielectric material.
According to a further exemplary embodiment of the present invention the second layer comprises a leadthrough in the region of the decoupling unit so as to provide pressure equalization between the resonator and the environment.
In this way bursting open or cracking of the multilayer arrangement may be prevented in the case of considerable fluctuations in temperature, which fluctuations might otherwise result in enormous pressure differentials between the interior of the resonator and the environment.
According to a further exemplary embodiment of the present invention the feed line is essentially integrated in the second layer.
In this way it may be possible to design both the decoupling unit and the feed line as integral units formed during the process of producing the supporting board. In this case there may be no need for any mechanical adjustment between the decoupling unit and the feed line because both may be already firmly integrated in the supporting board.
According to a further exemplary embodiment of the present invention the feed line is designed as a microstrip.
According to a further exemplary embodiment of the present invention the feed line is designed to conduct electromagnetic waves of a frequency of between 60 GHz and 100 GHz, wherein the decoupling unit is designed for decoupling electromagnetic waves of a frequency of between 60 GHz and 100 GHz from the feed line to the waveguide.
Thus, decoupling of high-frequency electromagnetic waves from a printed circuit board to a waveguide is stated, which decoupling may be designed to cope even with frequencies exceeding 60 GHz, without this resulting in problems relating to mechanical tolerances or adjustment.
According to a further exemplary embodiment of the present invention the waveguide transition is integrally produced in a single process of producing the printed circuit board.
According to a further exemplary embodiment of the present invention a fill level radar is stated that is designed for determining the fill level in a tank, comprising an antenna for transmitting and/or receiving electromagnetic waves, a feed device for feeding the electromagnetic waves to the antenna, wherein the feed device further comprises a waveguide for conveying the electromagnetic waves between the antenna and the feed line, and wherein the feed device comprises a waveguide transition as described above.
Such a fill level radar may not comprise an external resonator in order to couple the generated high-frequency waves into the waveguide. Instead, the resonator may be directly integrated in the printed circuit board. In this way tolerance problems associated with the installation of the resonator may be prevented. Furthermore, the number of mechanical components may be reduced, which in turn results in a reduction in installation expenditure. In particular, such a fill level radar is suitable also for high-frequency radiation exceeding 60 GHz.
According to a further exemplary embodiment of the present invention, by way of an attachment means, the waveguide is connected to the supporting board in such a way that the electromagnetic waves can be decoupled, by way of the decoupling unit, from the feed line to the waveguide.
Furthermore, the use of a waveguide transition according to the invention for fill level measuring is stated.
Moreover, a method for producing such a waveguide transition is stated, in which a first layer is provided, a resonator is created, in the first layer, for decoupling electromagnetic waves from a feed line to a waveguide, a second layer is created, and the feed line is essentially created in the second layer, for conducting the electromagnetic waves, wherein the resonator is integrated in the first layer.
In this way a method may be provided, by means of which integral production of the waveguide transition during the process of printed circuit board production may be provided. In this arrangement the resonator may form an integral part of the printed circuit board.
According to a further exemplary embodiment of the present invention the method further comprises the creation of a third layer, which is arranged between the first layer and the second layer, wherein the first layer is designed as an insulating printed circuit board substrate material, and wherein the third layer is metallic.
According to a further exemplary embodiment of the present invention the creation of the decoupling unit comprises an etching step, a milling step, or a laser drilling step, which if need be is followed by a metallization step.
Further exemplary embodiments of the invention are stated in the subordinate claims.